This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-033234, filed Feb. 10, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to an electroplating technique and, more particularly, to a plating method and plating apparatus for a semiconductor device.
In recent years, copper has received a great deal of attention as an interconnection material in order to reduce the interconnection resistance of an LSI and improve its reliability. The copper interconnection forming methods include CVD, sputter reflow, and plating. Of these methods, plating is simple in process and low in cost, exhibits high filling performance, and can form a high-performance interconnection.
However, currently available plating apparatuses do not satisfactorily consider a semiconductor device manufacturing process. The conventional apparatus basically adopts a xe2x80x9cplating bathxe2x80x9d method following the plating industry. According to this method, a semiconductor substrate is plated by dipping it in a plating bath or cup filled with a plating solution.
This classical plating method has not achieved progression particularly considering the semiconductor device manufacturing process. Thus, when the method is applied to the semiconductor device manufacturing process, the following serious problems arise.
(1) It is difficult to perform precise control of an absolute film thickness in nanometers that is much smaller than the film thickness in a general plating industry, and to ensure high uniformity on the substrate surface.
(2) Bubbles and dust greatly influence the semiconductor process to which a very low defect density on a fine pattern is demanded.
(3) A voltage/current from a cathode can only be applied from the periphery of a substrate outside a region where a pattern is formed. If the electrode is brought into contact with the inside of the substrate where the pattern is formed, scratches or dust is generated to decrease the product yield. This is disadvantageous in a situation in which the wafer size in the semiconductor process is increasing year by year. That is, the conductive layer of an electroplating solution must be made thick on the wafer surface. Otherwise, the resistance from the cathode potential supply portion at the periphery of the substrate to the center of the substrate increases, failing to ensure the plating current at the center. However, the thickness of the conductive layer is limited by process constraints.
(4) It is difficult to perform locally plating in accordance with a regular pattern formed on a semiconductor substrate. It is also difficult to perform positive control of the film thickness on the surface of a semiconductor substrate (wafer), for example, to make the periphery thick in accordance with requirements in a post-plating step (e.g., CMP). If the plating solution is not wanted to attach to the lower surface of the substrate in order to prevent contamination of the substrate or the like, a special seal must be used to protect the lower surface.
(5) In forming a film into a three-dimensional pattern, film formation on projections cannot be suppressed. An example of the most typical applications of a plating metal film among semiconductor processes is formation of a metal film for forming a damascene interconnection. In the damascene process, a plating metal is buried in an interconnection groove or hole, and a metal film formed outside the groove or hole is removed by CMP or the like. Considering load reduction in a subsequent CMP step or the like, formation of the plating film on a portion except for the groove or hole must be prevented as much as possible. The above-described requirements and problems unique to the semiconductor process obstruct the use of plating.
It is an object of the present invention to provide a plating method and plating apparatus which can easily perform precise control of the plating film thickness and are hardly influenced by bubbles and dust.
It is another object of the present invention to provide a plating method which realizes preferential formation of a plating film to a groove or hole suitable for the damascene process.
It is still another object of the present invention to provide a plating method and plating apparatus capable of performing local plating.
To achieve the above objects, according to the first aspect of the present invention, there is provided a plating method comprising the steps of
preparing a substrate to be processed which has a base plate and a conductive layer formed on at least part of the base plate,
applying a potential of a cathode to the conductive layer,
causing a first impregnated member containing a plating solution in electrical contact with an anode to face the conductive layer, and
relatively moving at least part of the first impregnated member with respect to the conductive layer in order to form a plating film on at least part of the conductive layer.
The step of relatively moving at least part of the first impregnated member with respect to the conductive layer desirably includes the step of vertically moving the at least part of the first impregnated member with respect to the conductive layer.
The step of vertically moving at least part of the first impregnated member with respect to the conductive layer desirably includes the step of moving the anode in contact with the first impregnated member apart from the conductive layer in accordance with plating of the plating film.
The step of vertically moving at least part of the first impregnated member with respect to the conductive layer may include the step of controlling at least one of a moving speed of relative movement in a vertical direction and an application current in accordance with plating of the plating film.
The step of vertically moving at least part of the first impregnated member with respect to the conductive layer desirably includes the step of forming a plating film while alternately repeating an operation of causing the conductive layer and the first impregnated member to face each other and an operation of dipping the first impregnated member into a plating bath containing the plating solution.
The step of connecting the cathode to the conductive layer desirably includes the step of connecting the cathode to the conductive layer by bringing a second impregnated member which contains an electrolytic solution and is connected to the cathode into facing the conductive layer in a different region from a region where the first impregnated member comes into facing the conductive layer.
The second impregnated member can perform the same relative movement as the first impregnated member.
The plating method desirably further includes the step of measuring a film thickness of the plating film by a film thickness measuring mechanism arranged on the conductive layer in a different region from a region where the first impregnated member comes into facing the conductive layer.
The plating method desirably further includes the step of additionally forming the plating film by bringing the impregnated member into facing the conductive layer in accordance with a measurement result of the film thickness measuring mechanism.
The film thickness measuring mechanism desirably performs the same vertical movement as the first impregnated member.
The step of vertically moving at least part of the first impregnated member with respect to the conductive layer can include the step of bringing at least part of the first impregnated member into contact with the conductive layer.
The step of relatively moving at least part of the first impregnated member with respect to the conductive layer can include the step of horizontally moving at least part of the first impregnated member with respect to the conductive layer.
The step of horizontally moving at least part of the first impregnated member with respect to the conductive layer desirably includes the step of bringing at least part of the first impregnated member into contact with the conductive member, and moving the plating solution on an upper surface of the base plate into the depression pattern formed in advance in the upper surface of the base plate by sliding movement.
According to the second aspect of the present invention, there is provided a plating method comprising the steps of
preparing a substrate to be processed which has a base plate and a conductive layer formed on at least part of the base plate,
applying a potential of a cathode to the conductive layer,
causing a first impregnated member containing a plating solution in electrical contact with an anode to face the conductive layer, and
forming a plating film on at least part of the conductive layer while controlling a film thickness profile.
The step of forming a plating film on at least part of the conductive layer while controlling a film thickness profile desirably includes the following steps:
1) the step of making a film thickness on a depression pattern of the base plate larger than a film thickness on an upper surface of the base plate, the base plate having the depression pattern on a surface thereof;
2) the step of controlling at least one of a stay time of the impregnated member on the conductive layer and an application current value supplied between the anode and the cathode;
3) the step of setting the anode having a desired pattern on the impregnated member;
4) the step of controlling a flat distribution of a current flowing through the conductive layer by either one of an electrode and an insulator with a desired pattern formed inside the impregnated member;
5) the step of using the impregnated member having a desired two dimensional distribution of a supply amount of plating solution to the conductive layer.
6) the step of relatively moving the impregnated m ember and an upper surface of the base plate in a facing plane direction, thereby decreasing the plating solution on the upper surface of the base plate, the base plate having a depression pattern on the surface; and
7) the step of bringing part of the impregnated member into contact with the conductive layer and controlling a film thickness in accordance with whether the impregnated member is in contact with the conductive layer.
According to the third aspect of the present invention, there is provided a plating method comprising the steps of
preparing a substrate to be processed which has a base plate and a conductive layer formed on at least part of the base plate,
applying a potential of a cathode to the conductive layer, and
forming a plating film on at least part of a region by causing an impregnated member containing a plating solution in electrical contact with an anode to face the conductive layer,
wherein the step of forming a plate film includes the step of forming a plating film while alternately repeating an operation of causing the conductive layer and the impregnated member to face each other and an operation of moving the impregnated member to a remote location where a plating current is interrupted between the anode and the cathode.
The operation of moving the impregnated member to a remote location desirably includes an operation of dipping the impregnated member into a plating bath containing the plating solution.
According to the fourth aspect of the present invention, there is provided a plating method comprising the steps of
preparing a substrate to be processed which has a base plate and a conductive layer formed on at least part of the base plate,
causing an impregnated member containing a plating solution in electrical contact with an anode to face the conductive layer in order to form a plating film in at least part of a region, and
connecting a cathode to the conductive layer by causing another impregnated member which contains an electrolytic solution and is connected to the cathode, to face the conductive layer in a different region from a region where the impregnated member comes into contact with the conductive layer.
The conductive layer may be in contact with at least one of the impregnated member and the another impregnated member.
The another impregnated member can perform the same sliding movement as the impregnated member.
According to the fifth aspect of the present invention, there is provided a plating method comprising the steps of
preparing a substrate to be processed which has a base plate and a conductive layer formed on at least part of the base plate,
causing an impregnated member containing a plating solution in electrical contact with an anode to face the conductive layer in order to form a plating film in at least part of the conductive layer,
connecting a cathode to the conductive layer by causing another impregnated member which contains an electrolytic solution and is connected to the cathode, to face the conductive layer in another region than a region where the impregnated member faces the conductive layer, and
measuring a film thickness of the plating film by a film thickness measuring mechanism arranged on the conductive layer in still another region than a region where the impregnated member faces the conductive layer.
The plating method desirably further includes the step of additionally forming the plating film by causing the impregnated member to face the conductive layer in accordance with a measurement result of the film thickness measuring mechanism.
The film thickness measuring mechanism desirably performs the same horizontal movement as the impregnated member.
According to the sixth aspect of the present invention, there is provided a plating apparatus for forming a plating film on a conductive layer formed on at least part of a surface of a substrate, comprising
a power supply for supplying an anode potential and a cathode potential, the cathode potential being applied to the conductive layer,
an anode for receiving the anode potential,
a first impregnated member which has a first and a second major surface, is in contact with or faces at least a partial region of the conductive layer on the first major surface, is in contact with the anode on the second major surface, holds a plating solution, and supplies the plating solution to the conductive layer,
a plating solution supply mechanism for supplying the plating solution to the first impregnated member, and
a first controller for controlling formation conditions of the plating film.
The plating apparatus desirably further includes the following arrangements.
1) The plating apparatus further comprises a second controller for controlling a gap between the substrate and the first impregnated member facing the substrate in accordance with plating of the plating film.
2) The plating apparatus further comprises an insulating member formed to surround a side portion of the first impregnated member and a side portion of the anode in contact with the second major surface of the first impregnated member, and a second impregnated member which is adjacent to the first impregnated member through the insulating member, holds an electrolytic solution, supplies the electrolytic solution to the conductive layer, and receives the cathode potential.
3) The plating apparatus further comprises an insulating member formed along a side surface of an opening formed through the first impregnated member and the anode in contact with the second major surface of the first impregnated member, and a second impregnated member which is formed in the opening through the insulating member, holds an electrolytic solution, supplies the electrolytic solution to the conductive layer, and receives the cathode potential.
4) The plating apparatus further comprises a first moving mechanism for changing relative positions of the conductive layer and the first impregnated member in a contact or facing plane direction.
5) The anode has at least one through hole, and the plating solution supply mechanism supplies the plating solution to the first impregnated member through at least one through hole formed in the anode.
6) The plating solution supply mechanism comprises a plating bath filled with the plating solution, and a second moving mechanism for moving the first impregnated member in contact with or facing at least the partial region of the conductive layer, and dipping the first impregnated member in the plating bath.
7) The plating apparatus further comprises a sensor for sensing a gap between the anode and the conductive layer, and a third controller for adjusting the gap between the anode and the conductive layer in accordance with a detection result.
8) The plating apparatus further comprises a composition sensor for sensing a composition ratio of the plating solution contained in the impregnated member, and a composition adjusting unit for adjusting a composition of the plating solution for the impregnated member in accordance with a sensing result of the composition sensor.
9) The plating apparatus further comprises a fourth controller for controlling at least one of a stay time during which the impregnated member stays on at least part of the conductive layer, and an application current value between the anode and the conductive layer.
10) The anode is formed with a desired pattern.
11) The plating apparatus further comprises either one of an electrode and an insulator with a desired pattern formed inside the first impregnated member.
12) The first impregnated member has a desired distribution as a supply amount distribution of the plating solution to the conductive layer.
13) The plating apparatus further comprises a fifth controller for slightly vibrating the first impregnated member up and down, and right and left upon energization.
14) The plating apparatus further comprises at least one strainer arranged inside the first impregnated member, near a facing portion between the first impregnated member and the conductive layer, in order to drain-the plating solution.
With these arrangements, the present invention attains the following operation effects.
According to the plating method of the present invention, an impregnated member containing a plating solution is placed on a substrate to be processed. An anode is set on the impregnated member, whereas a cathode is connected to the substrate. Unlike the plating bath method, the plating method of the present invention can control the plating rate of a plating film to be formed, by controlling the stay time of the impregnated member on a member to be plated, the application current value, the pattern of the anode, the pattern of an intermediate electrode or insulator formed in the impregnated member, or the supply distribution of the plating solution to the impregnated member. This facilitates control of the plated thickness.
A through hole is formed in the anode, and bubbles in the plating solution held by the impregnated member can be removed to suppress defects of the plating film caused by the bubbles. Further, the impregnated member and substrate are relatively moved in the direction of the contact plane. This prevents bubbles or dust in the plating solution supplied to the substrate surface from staying at one portion. Defects of the plating film are therefore suppressed.
If plating using the impregnated member is done for a conductive layer formed on a substrate surface having a depression pattern of grooves or holes, the plating solution stays in the depression, and the supply amount of plating solution to the depression becomes larger than on the upper surface of the substrate. Hence, the plating rate of the plating film on the surface of the depression becomes higher than on the upper surface of the substrate. Preferential formation of the plating film in the groove or hole can be realized to form a plating film suitable for the damascene process. By relatively moving the impregnated member and substrate in the direction of the contact plane, the surface of the plating film formed on the upper surface of the substrate is mechanically polished by the impregnated member. More preferential formation of the plating film in the groove or hole can be achieved.
Even if the impregnated member is not in contact with the substrate to be processed, a dynamic pressure is generated in the plating solution due to relative movement. A pressure difference between an inside and an outside of the depression caused by the dynamic pressure can make the plating rate greater in a groove or a hole than that on the upper surface of the substrate.
The depression in the surface of the plating film formed finally is shallower and smoother than the depression in the substrate, which facilitates a subsequent smoothening step using chemical mechanical polishing.
The plating solution can be selectively supplied to the substrate surface using an impregnated member smaller in size than the substrate. Consequently, a plating film can be locally formed. Since the plating film is formed at only a portion on the substrate where the anode exists, the plating film can be locally formed even using an anode of a desired pattern.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.